Download Probability and Heredity 2013

Probability and Heredity
EQ: How does probability affect the
way traits are inherited?
Previously, in life science…
• You learned that alleles for traits are
inherited according to definite patterns.
Now, you will discover the mathematical
foundation for these patterns.
1. What is Probability?
• The likelihood that a particular event will
occur.
• Coin Toss (20X)
H
T
prediction
actual
• Probability predicts what is LIKELY TO
OCCUR…Not necessarily what will occur
• Each event occurs INDEPENDENTLY
What is probability?
A number that describes how
likely it is that a certain event will
occur
2. What are Punnett Squares?
• Chart used to show possible allele
combination
What is a Punnett square?
A chart that shows all the
possible combinations of alleles that
can result from a genetic cross.
3. How do you use Punnett squares?
Show possible
combination
1. Draw a square.
Divide it into 4
sections.
2. One parent’s alleles
on the top
3. One parent’s alleles
on the side
4. Cross alleles (like
multiplication!)
What is the probability that an
offspring will have white fur?
0% !
What is the probability that an
offspring will have black fur?
100% !
4. What is phenotype?
• An organism’s appearance, or visible traits.
• Example: Purple or white flowers
5. What is genotype?
• An organism’s genetic makeup, or allele
combinations.
• Example: PP or Pp or pp
6. What is homozygous?
• having 2 identical alleles
example: PP or pp
7. What is heterozygous?
• having 2 different alleles
example: Pp
8. Make a chart showing the
genotypes and phenotypes
B = Brown; b = blue
genotype
phenotype
Homozygous
or
Heterozygous?
8. Make a chart showing the
genotypes and phenotypes
B = Brown; b = blue
genotype
BB
B___
b ___
phenotype
Homozygous
or
Heterozygous?
How many genotypes are there for the
smooth-pod phenotype?
Two!
9. Cross homozygous brown (BB)
with a homozygous blue (bb)
9. Example #1
Cross homozygous brown (BB) with a homozygous blue
(bb)
B
B
b
b
Genotype:
BB =
Bb =
bb =
Phenotype:
Brown eyes =
Blue eyes =
9. Example #1
Cross homozygous brown (BB) with a homozygous blue (bb)
B
B
Bb
Bb
Bb
Bb
b
b
Genotype:
BB = 0/4 or 0%
Bb = 4/4 or 100%
bb = 0/4 or 0%
Phenotype:
Brown eyes = 4/4 or 100%
Blue eyes = 0/4 or 0%
10. Cross heterozygous brown (Bb)
with a heterozygous brown (Bb)
Example #2
Cross heterozygous brown (Bb) with a heterozygous brown
(Bb)
B
b
BB
Bb
Bb B
Bb
Bb
bb
b
Genotypes:
BB = 1/4 or 25%
Bb = 2/4 or 50%
Bb = 1/4 or 25%
Phenotypes:
Brown = ¾ or 75%
Blue = ¼ or 25%
11. How is probability related to
genetics?
• Mendel discovered that probability can be used
to predict the results of genetic crosses!
• Probability is used to PREDICT the
RESULTS of a genetic cross
12. What is codominance?
• Neither allele is dominant or recessive, both
alleles are expressed in the offspring.
Will the offspring be heterozygous or
homozygous?
heterozygous! They have alleles
for white and black feathers.
DISCLAIMER:
ROOSTER NEED TO MATE WITH A
CHICKEN NOT ANOTHER ROOSTER!